From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH rdma-core] mlx5: Return pointer to CQ doorbell Date: Thu, 17 Aug 2017 11:33:20 -0600 Message-ID: <20170817173320.GB22792@obsidianresearch.com> References: <1502976998-20906-1-git-send-email-yishaih@mellanox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1502976998-20906-1-git-send-email-yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Yishai Hadas Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, leonro-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org, majd-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org List-Id: linux-rdma@vger.kernel.org On Thu, Aug 17, 2017 at 04:36:38PM +0300, Yishai Hadas wrote: > From: Leon Romanovsky > > The returned UAR pointer is actually void ** and points to whole > UAR database. > > Because user is not supposed to access it and expected to use > the CQ doorbell, we will return uar[0] (CQ doorbell) directly > and eliminate the following logic in the applications: > > uint64_t cq_db_reg = (uint64_t *)(((uint64_t)(uint64_t *)rxq->cq_uar) + > MLX5_CQ_DOORBELL; NAK, at least, as is.. This changes the ABI and mlx5dv is a public interface now, so you have to do it properly. Looking at it, my advice is to rev the symbol version of mlx5dv_init_obj and consider providing a compat symbol. Also, you need to change the name of the 'uar' field: > - cq_out->uar = mctx->uar; > + cq_out->uar = mctx->uar[0]; To something else, to make it clear, which of the two ABIs the application code is coded to - for a change like this, you *MUST* force old apps to have a compile failure. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html